Chusetts



, (No Model.)

J. HUGHES. SAFETY VALVE.

No. 593,526. Patented Nov. 9,1897.

UNITED STATES PATENT OFFICE.

JOHN HUGHES, OF SOMERVILLE, MASSACHUSETTS,'ASSIGNOR TO THE CROSBY STEAM GAGE AND VALVE COMPANY, OF BOSTON, MASSA- CHUSETTS.

SAFETY-VA LVE.

SPECIFICATION forming part of Letters Patent No. 593,526, dated November 9, 1897. Application filed May 14, 1896. Serial No. 591,567. (No model.)

To all whom it may concern.-

Be it known that I, JOHN HUGHES, a citizen of the United States, residing at Somerville, in the county of Middlesex and State of Massachusetts, have invented certain new and useful Improvements in Safety-Valves; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to an improvement in a device for overcoming or neutralizing the expansion of a cylinder of one kind of metal, as brass, when screwed into another cylinder of another kind of metal of less expansion.

In the drawings, Figure 1 represents the invention as adapted to the valve and valve proper of the ordinary safety-valve, known popularly as the Crosby Meady safetyvalve, shown in vertical section. Fig. 2 represents that portion of Fig. 1 marked B in perspective with the ring of wire below it.

In the drawings, A represents the base of this safety-valve, which in this case is of castiron. It has a circumferential recess with a vertical side in which are out screw-threads a. The bottom of this recess a has a horizontal face substantially at right angles with the side.

B represents the valve-seat, of brass or similar metal, of cylindrical form, having extern al screw-threads 6 upon its perpendicular side. These screw-threads are of the same character as those out in the recess in the cast-iron base and are made to fit therein. The bottom 11 of this valve-seat B is faced off to fit the horizontal part of the valve (1, having the outer wall made by the. channel slightly shorter than the inner one. The valve-seat B has a central cylindrical portion 7), sustained by the horizontal arms 19 1), projecting inwardly from the inner part of the valve-seat B to it. This inner cylinder performs the office of guiding the valve 0, which rests upon the valve-seat B at its seat 0' c, by means of its guides c c.

It has been found in practice that when two cylinders of different metals, as above described, have been screwed together, as shown, are subjected to a high degree of heat arising from steam on account of the greater expansion of the brass cylinder than that of the outer iron cylinder the former is cramped or distorted thereby, so that it is often difticult to make the surfaces at the seat 0 c tight to prevent leakage of the steam through it. This is often so, although when the temperature is low the seat will then be tight. Especially is this the case when the seat B has its guiding-cylinder, such as is shown herein, supported by the horizontal arms projecting from the interior face or wall of such valve. To overcome this tendency to distortion and consequent leakage at the seat a c, it is found that by cutting a narrow circumferential channel b in the wall of the valveseat B the expansion of the arms I) b, as wellas that of the cylindrical portion of the valveseat B, is 'taken up or neutralized by such channel and not transferred to the outer part of the wall of the valve-seat B nor .to the upper part of the valve-seat B, where it makes its contact by its seat 0 c with the valve 0, there resting upon it. Continuous and longtried experiment and use fully sustain this view. Valves which it was almost impossible to render tight at the seat 0 0 when subjected to steam under a high pressure, and thus great heat due thereto on account of the difference of expansion between the iron valve-casing A and the Valve-seat B, were immediately made useful by being relieved of this unfortunate condition by simply cutting the channel above described and shown at b To sustain the walls of the valve-seat B where the channel is made, a wire 12 is inserted in the lower part of it, as shown. there is left sufficient space for expansion without injurious effects arising therefrom. The walls forming this channel have the outer one slightly shorter than the inner one, so that while the seat or tight joint is made between the latter one and the iron the former can yield to the influence of temperature.

It is said that hours sometimes have been expended in the making of a large valve tight at the seat 0 0', due to the distortion of the valve-seat B, arising from the unequal ex pansion of the two metals which compose the casing and the valve. Upon trial and leakage found the valve was dismantled, the seats reground where found to be distorted,

By this means and again tried, and so on by repeated trials until they might at last be made tight at the pressure of steam at which they were to be used; but it so happens that upon any material change of pressure from this new distortions would take place, and they would be compelled to be ground again under repeated trial before they could be made tight.

The present invention is not only valuable in safety-valves, but may be used wherever two cylinders are brought together, as shown,- made of metals of different expansion and contraction.

Having thus described my invention, what I claim is- 

